Gas detectors using treated tape to measure gases are known in the art. For example, some gas detectors using treated tape can measure a low concentration gas that comes into contact with the tape.
In known gas detectors, the treated tape can include a chemically treated paper that reacts to a target gas flow delivered by, for example, a sample extraction system inside of the gas detector. The treated tape can react to the gas flow by changing color at the spot where the target gas contacts the tape.
Different types of target gas can cause different color stains on the tape. Similarly, different concentrations of the target gas can alter the color stains on the tape. For example, a higher concentration of target gas can produce a darker stain.
Known gas detectors using treated tape to measure the concentration of gases have incorporated an LED. The LED can have a calibrated intensity and can act as a source of light directed onto the tape. The reflection of light from the tape, and any stains thereon, can be measured by a photodiode. Thus, the darkness of the stain can be measured and the concentration of the target gas can be determined.
Some known gas detectors using treated tape have only employed single wavelength LEDs. Single wavelength LED gas detectors have a high sensitivity to a single stain color caused by one particular type of gas. That is, single wavelength LED gas detectors are highly sensitive to detecting a single type of gas because the wavelength of the LED is calibrated for the particular tape color caused by the one particular type of gas. However, these single wavelength LED gas detectors have a reduced and/or minimal sensitivity to stain colors caused by other types of gas. Thus, single wavelength LED gas detectors have a poor sensitivity for detecting multiple types of gas.
Therefore, there is a continuing, ongoing need for gas detectors that detect multiple types of gases. Preferably, these gas detectors use an adjustable color source and wavelength spectrum analysis.